Hollow space radiator



May 30, 1944.

W. DALLENBACH HOLLOW SPACE RADIATOR Filed Aug. 22, 1940 WA: 75/?cine-Nana,

Patented May 30, 1944 2,349,942 HOLLOW SPACE nAmA'ron Walter ApplicationAugust 22 In Germany tuned hol- This invention particularly can be usedas sending or receiving aerial for oscillation having a wave length lessthan 1 meter.

- One feature of this invention is the tuned hollow space radiatorconsisting of surrounding conducting surfaces and open at one side, thehollow space being coupled to an energy conducting device or alike bymeans of a slit in the back wall of said hollow space radiator. Severalof such hollow space radiators are coupled side by side to an energyconducting device, or alike for the purpose of improving the directingeffect. The length of these single radiator is equal to the length of asingle wave or a multiple of one wave length. It is necessary that thesingle radiators of such a group be tuned accurately so as to createsignals of frequency so a to obtain optimum results.

A further feature of this invention is that the single radiator wallsmay be placed directly adjacent one another and that they can be coupledelectrically through openings of the walls thus providing an automaticadjustment of the different radiators. In this way the adjusting of thesingle radiators by hand, which is rather dimcult and troublesome, canbe avoided. Furthermore the location of the slits in the back walls ofthe single radiators forming the connections to the energy conductingdevice is not critical.

Fig. 1 represents a single hollow space radiator consisting of a boxlikedevice.

Fig. 2 shows a group radiator consisting of several hollow spaceradiators located adjacent one another and provided with openings in theside walls.

Fig. 3 illustrates a plan view of a set of hollow space radiatorsforming a group as shown in Fig. 2, and showing the side walls of thesingle hollow space radiators, each being divided into two portions atthe outside, each portion forming a small pocketlike case having a depthof one quarter of a wave length.

Fig. 1 represents the hollow space radiators consisting of a box withparallel walls, the walls having conducting surfaces. The side edges ofthe box are designated a, b and c, respectively, the front of the boxbeing open. The back wall of the box contains a slit 2 communicatingwith the interior of an energy conducting device 6; said device may ormay not be provided with an inner conductor. The hollow space radiatorthus Dallenbach, Berlin, Germany; vested in the Alien Property Custodiane 1940, Serial No. 353,755 August 22, 1939 3 Claims. (Cl. 250-11) iscoupled with the energy conducting device and is excited in such waythat theelectric vector of the oscillations is perpendicular to thewalls having edges be. The intensity of th electrical vector is dividedsinusoidal alongthe edge 0 as along the edge has shown in Fig. l bythecurves e and f. A box tuned in'such'a way represents a resonatorbeing equivalent to a Lecher system of a length of one quarter of .awave length. In. the open front side lfthere is a potential loop, therebeing. apoteritial node in the back wall at the slit 2. The tuning ofthe box will not be changed by alteration of the length of the edge a.

Fig. 2 represents another special feature of the invention, this being agroup radiator, consisting of several single boxes as shown in Fig. 1.This group radiator is shown with its edge a very much longer than theother edges b and c. In this group radiator box several separating andelectrical conducting walls 1 are provided parallel to the sides bc,thus forming a device comprising a set of single radiators built closelytogether. Every single radiator box in its back wall has a slit 2, forcoupling the box to the energy conducting device 6. The wall 1 containopenings 9 for providing a radiation of only one wave length. Theseopenings should be particularly placed close to the back walls 8 of thegroup box while these openings are shown semicircular, it also may beuseful to form these openings 9 rectangularly by leaving off that smallpiece of a separating wall 1 which is next to the back wall 8, i. e. therear end of the separating wall being spaced from the back wall. Thecoupling of the single radiators resulting from these openings 9 in theside walls 1 provides, in all the boxes, equal amplitudes ofoscillations even if the excitation of the different slits 2 in thesingle boxes is not exactly the same. Therefore it is not necessary toplace the slits 2 with respect to the energy conducting device, in amathematically exact position in the current loops. In many cases it isquite sufiicient that the slits 2 be placed near to currents of equaldirection, 1. e. having a distance of about one wave length. In somecases it might be necessary to regulate the coupling of the singleradiators and therefore it will be useful to provide adjustable openings9 in the nature of a variable screen. Instead of building only one largebox containing separating walls for making a radiator device, one alsocan put together several single boxes each box comprising one hollowspace radiator. The construc-. tion as per Fig. 2 has essentialadvantages.

Fig. 3 schematically shows a modification of the Fig. 2 arrangementdesigned to avoid spraying appearing at the edges of the walls asexplained in applicants former application filed February 18, 1936, Ser.No. 64,604. In Fig. 3 the edges of the surfaces next to the front side,especially the side walls It and the separating walls I, and also thecovers 12 and the grounds l3 (-Fig. 2) are split thus to providepocket-like small cases ll oil a depth of one quarter of a wave length.Thus, at all edges of the front sides the intensity of the current willbe exactly zero, since the spaced wall of each of the pockets form aLecherconductor one quarter of a wave length, the spaced. walls thereofbeing connected at the inner ends thereof. According to circuitequations, a Lecher concluctor one fourth of a wave length, shortcircuited' at the end, has a final resistance that is zero in magnitude,whereas the initial resistance. that occurs at the free end of the boxamounts to infinity. Therefore no current can flow in this Lecherconductor of a quarter wave length so that overlapping of the currentfrom the inside of the box on the outer' surfaces is prevented.

-What I claimis:

l. A device 'forradiating ultra short waves particularly of a wavelength of less than 1 meter, comprising at least two tuned hollowspaces, defined by a plurality of walls having conducting surfaces, saidhollow spaces being closely adjacent one another, the walls between thesingle hollow spaces having openings therethrough whereby to couple thehollow spaces electrically, said hollow spaces being coupled to anenergy conducting device by means of slits in the back walls of theradiator.

2. A device for radiating ultra short waves particularly of a wavelength of less than 1 meter, comprising at least two tuned hollow spacesdefined by a plurality of, walls having conducting surfaces, said hollowspaces being closely ad- 'jacent one another, the walls between thsingle hollow spaces having openings therethrough whereby to couple thehollow spaces electrically, said walls at the front edges being providedwith pocketlike cases of the depth of one quarter the wav length beingresonated.

3. A device for radiating ultra short waves, particularly of a wavelength of less than 1 meter, comprising at least two tuned hollow spacesdefined by a plurality of walls having conducting surfaces, said hollowspaces being closely adjacent one another and adjacent spaces having onewall in common, the wall between the single hollow spaces havingopenings therethrough whereby to couple the hollow spaces electrically,said hollow spaces being defined by-a boxlike device with parallelwalls, said boxlike device being open at one side and having a breadthsubstantially longer than the length and depth and being divided bywalls in several single radiators.

WALTER. DALLENBACH.

